1. Technical Field
Various embodiments relate to a semiconductor apparatus, and more particularly, to a resistive memory apparatus and an operation method thereof.
2. Related Art
Resistive memory is being highlighted as the next generation of memory having advantages such as low cost, random access, high speed operation, low power consumption and nonvolatile properties.
Resistive memory has a data storage material layer disposed between a pair of electrodes, and stores data by changing the resistive state of the data storage material layer through application of current or a voltage.
Phase change memory, a type of resistive memory, includes an access element, a bottom electrode formed on the access element, and a data storage material layer or a resistor element formed between the bottom electrode and a top electrode. If the access element is driven through a word line to write data in the phase change memory, as write current is applied from a bit line to the resistor element, the resistive state of the resistor element may change between a crystalline state (a low resistive state) and an amorphous state (a high resistive state).
Heat is generated while writing to phase change memory cells and this heat may reach neighboring cells. If the neighboring cells are in the resistive state, or are storing data, and the temperature of the neighboring cells reach the crystallization temperature, the resistive state of the neighboring cell may change. This is referred to as a disturbance phenomenon.
Further, if phase change memory cells spend a given amount of time at a certain temperature, the data storage material in the high resistive state is crystallized and data may be erased.
FIG. 1 is a diagram illustrating a disturbance phenomenon of a resistive memory apparatus. In FIG. 1, the reference symbol BE represents the bottom electrode, TE the top electrode, and PCM a phase change material acting as the data storage material.
As shown in FIG. 1 (a), during the writing operation on a selected cell, heat is radiated to an adjacent cell, which is in an amorphous state.
Also, as shown in FIG. 1 (b), where the write operation for the selected cell is repeated a certain number of times, the adjacent cell is likely to be crystallized.
That is, as the write operation is repeated for the selected cell, the data of the adjacent cell is deleted due to the disturbance phenomenon.
With time, the resistive state of an adjacent cell, written to an amorphous state and repeatedly exposed to heat radiated from a selected cell, is crystallized to be in a low resistive state. Also, the resistive state of an adjacent cell is influenced by write pulse duration for the writing operation on a selected cell, and the distance from the selected cell to the adjacent cell.